The present invention relates to a system for dispensing particulate matter onto a substrate, and more particularly to a rotating drum seeder for placing sesame seeds onto a plurality of buns traveling at a high rate of speed along a conveyor.
The use of seed-depositing devices is well known in the art. In various food processing applications, these devices are used to introduce seeds and related edible flavorings to bakery products, such as rolls, loaves of bread and sandwich buns. In the production of seeded sandwich buns, a continuous conveyor, often carrying trays containing a number of buns, is passed under a seed-dispensing device including a spreader connected to a seed hopper. Typically, the spreader includes an inlet section which receives a continuous flow of seed from the seed hopper, and a toothed auger to agitate and dispense the seeds onto buns passing beneath on a conveyor. In order to manufacture large quantities of finished product in a timely fashion, such as for a restaurant or retail grocery store, the process must have a high throughput, thereby necessitating high-speed conveying and deposition methods. An unfortunate concomitant to this requirement is that the quantity of seeds placed on the surface of each bun can be highly non-uniform, resulting in an aesthetically unappealing, and possibly unappetizing final product. Furthermore, seed spillage and related inability to control seed-dispensing patterns results in substantial amounts of feedstock waste. The requirement for speed, as well as reliance on gravity as the final stage in the deposition process, has worked a detriment to the prior art systems.
Accordingly, there is a need for a device that overcomes the above problems by uniformly and repeatably dispensing seeds in closely regulated amounts with a minimum amount of wasted feedstock. Furthermore, there is a need for a device that eliminates or reduces reliance on gravity-based deposition techniques, in order to satisfy the ever-increasing need for simpler, cheaper, more reliable seeding devices.
This need is met by the present invention wherein a rotary drum seeder is disclosed that overcomes many of the problems associated with the prior art. In accordance with one embodiment of the present invention, a rotary drum assembly for depositing particulate matter on a substrate is disclosed. The assembly includes a rotatable drum with a substantially hollow internal portion and an axis of rotation along the drum length. In the present context, the term xe2x80x9csubstantiallyxe2x80x9d implies that, while the article is generally as described, the description requires something less than exact correspondence. For example, the inclusion of other components (such as support structure, fluid conduit and the like) in the internal cavity of the drum does not defeat its hollow nature merely because something less than 100% of the interior is available for the placement of a fluid or vacuum. A matrix of repeating patterns are formed on an outer surface of the drum, and each of the patterns are defined by a plurality of apertures, each of which are connected to the internal surface of the drum by a tubular bore, thereby ensuring fluid communication therethrough. The substantially hollow internal portion of the rotatable drum is capable of supporting at least a partial vacuum, which can be accomplished by placing the substantially hollow internal portion in fluid communication with a negative fluid pressure source, such as a vacuum pump. A particulate dislodging device operating locally within the drum""s internal portion exposes the apertures passing by that locality to a fluid overpressure. This overpressure is sufficient to overcome adhering forces present in the substantially hollow internal portion. Thus, upon applying a vacuum to the substantially hollow internal portion of the rotatable drum, particulate matter is drawn into operative contact with the apertures on the drum surface, where they stay until such time as the drum rotates to put the particulate-holding apertures into operative communication with the particulate dislodging device, whereupon the particulate matter is forcibly dislodged from the apertures by the particulate dislodging device.
Optionally, a main drive is coupled to the rotatable drum to effect drum rotation. The main drive may be either constant speed or variable speed. A clutch may be included to permit the drum to rotationally decouple from the main drive periodically. The clutch, for example, may be of the single rotation variety, such that after each complete particulate-dispensing cycle, the drum comes to at least an intermittent stop. Also, quick-release couplings and axial mounting can be used to ensure rapid drum assembly interchangeability to accommodate different aperture patterns on the drum surface. The apertures can further be dimpled to facilitate better particulate matter holding. The particulate dislodging device can be a positive fluid pressure device that is in fluid communication with a high pressure fluid source, such as that coming from a pressurizing pump. The drum also may include a stationary mandrel to establish differential pressure fluid communication between a vacuum source and the internal hollow portion of the drum, as well as between a high pressure source and the positive fluid pressure particulate dislodging device. In this capacity, the differential pressure fluid provided through the stationary mandrel includes both positive and negative pressure fluid. In the present context, a differential fluid pressure source, such as a pump, can be a source for either positive fluid pressure, negative/vacuum fluid pressure, or both simultaneously. The mandrel may further include a plurality of coaxial annular chambers for fluid communication, thus permitting an efficient fluid pressure carrying structure to operate substantially within the internal portion of the drum.
In accordance with another embodiment of the present invention, a rotary drum seeder for placing a plurality of seeds on the surface of foodstuffs is disclosed. The seeder comprises a primary support structure, a controller, a hopper for holding a quantity of seeds, a gate disposed between the seed hopper and a hopper discharge, and a rotary drum assembly in seed communication with the hopper discharge. By xe2x80x9cseed communicationxe2x80x9d, the hopper discharge and the rotary drum assembly are placed in relation to one another such that the addition of a quantity of seeds establishes a contiguous connection therebetween. The rotary drum assembly is identical to that of the previous embodiment, where references to the particulate matter in this embodiment specifically pertain to edible seeds, such as sesame seeds. Thus, upon operation of the rotary drum seeder, the seeds are drawn into operative contact with the apertures until such time as the rotary drum rotates the seeds to be in operative contact with a seed dislodging device, whereupon the overpressure causes the seeds to be forced from the apertures and deposited onto foodstuffs passing beneath.
Optionally, the seed dislodging device disposed within the rotary drum is a pressure shoe. The pressure shoe, which provides a continuous supply of pressurized fluid, dislodges the seeds when the dimpled seed cavities disposed on the outer surface of the drum pass over the shoe, thereby permitting an intermittent burst of pressurized fluid to pass through a tubular bore that connects the cavity to the substantially hollow internal portion of the rotary drum assembly""s rotatable drum, thus overcoming seed adhesion caused by the internal vacuum action. The rotary drum seeder optionally includes an air knife disposed between the hopper discharge and the rotary drum. The air knife uses a sheet-like air scraper to shake loose extra seeds adhering to the drum surface caused by residual vacuum around the apertures. This ensures that a consistent, repeatable quantity of seeds is deposited on the target food substrates. To ensure that an adequate supply of seeds is reaching the hopper discharge through the gate, an optional hopper agitator or vibrator may be added. This is valuable in situations where the seeds, which by virtue of their shape or hygroscopic nature, could stick together and would otherwise inhibit their normal free-flow from the seed hopper to the hopper discharge. The primary support structure of the rotary drum seeder may also include mounted wheels to enhance system portability. Similarly, a rotary drum height adjuster can be included to adjust to varying conveyor heights. Such adjuster is operatively responsive to user input, and can include hydraulic adjustment features to facilitate ease of use. Furthermore, as with the previous embodiment, the drum is readily interchangeable by axial removal and quick-release coupling features. This feature is advantageous in situations where different patterns to be deposited on the food substrate are desired. The rotary drum seeder may also include a stationary mandrel disposed substantially in the drum""s internal portion, in a manner similar to that of the previous embodiment. In the present embodiment, the mandrel includes a vacuum port and a pressure port to fluid connect the substantially hollow internal portion of the drum and the seed dislodging device to the vacuum source and the pressurized fluid source, respectively.
The rotary drum seeder of the present embodiment can also be synchronized with a foodstuff transporting apparatus, such as a moving conveyor, so that, upon detection of the arrival of a batch of food substrates, the rotary drum seeder can be made to perform one or more seed-dispensing cycles. This could be accomplished with a conventional motion or proximity sensor such that upon arrival of a container or the like holding the foodstuff to be coated, a signal can be sent to the controller to direct the rotary drum to advance a predetermined amount (such as one rotation) in order to deposit seeds onto the foodstuffs with minimal waste.
In accordance with yet another embodiment of the present invention, a method of depositing seeds on the surface of a plurality of food substrates is disclosed. The method includes the steps of placing seeds in a seed hopper, where the seed hopper is in seed communication with a rotary drum; adjusting a gate to permit seeds to flow from the seed hopper and into operative contact with a surface of the drum, which contains repeated patterns disposed thereon, each pattern comprising a plurality of individual apertures; establishing vacuum communication between the rotary drum and a vacuum source; establishing pressure communication between a seed dislodging device disposed within the rotary drum and a high pressure source; establishing operative connection between a main drive and the rotary drum; activating a main drive to prepare the drum for rotation; activating vacuum and pressure sources necessary for preferentially adhering and dislodging the seeds to and from the drum surface; detecting with a signal-sending sensor the presence of a transporting pan containing the plurality of food substrates; and rotating the drum in response to a signal received from the signal-sending sensor, where the rotation of the drum is timed to match the speed of the transporting pan. The step of creating a vacuum within the drum and establishing vacuum communication between the vacuum and the seeds causes the seeds to adhere to the plurality of apertures and adjacent areas. The drum is rotated to place more of the seeds into operative contact with more of the repeating patterns, and excess seeds are removed from the surface of the drum. The transporting pan is brought into alignment with a seed dislodging device disposed within the rotary drum such that when the seeds adhered to the apertures in the drum surface are moved within operative proximity to the seed dislodging device, the seeds are forced out of the apertures by the seed dislodging device, and deposited onto the food substrate disposed within the transporting pan.
Optionally, the step of removing excess seeds from the external surface of the drum can be accomplished with a boundary layer air knife or similar approach, which can be used to return the excess seeds to a hopper discharge disposed between the seed hopper and the rotary drum such that they remain in seed communication with the rotary drum, rather than spill or otherwise be wasted. Another option involves the use of a conveyor to transport the pan containing the food substrates. Furthermore, the apertures in the surface of the rotary drum may consist of dimpled cavities to minimize the risk of seeds becoming caught or wedged in the apertures, thereby ensuring better, more uniform seed adhesion. In addition, the seed-dispensing mechanism is a pressure shoe that effects separation of the seeds from the surface of the rotary drum by overcoming the vacuum inside the drum through the pressurized gas forced through the apertures. An additional step can include stopping the rotary drum after each complete revolution such that it can await the passage of another pan, achieving a stepped, rather than continuous rotation of the drum. This stepped rotation can be achieved through the use of a single-rotation clutch coupled to the main drive. Another additional step could include coating the food substrate with an adhesion-enhancing substance (such as a water mist) prior to depositing the seeds onto the substrate, to enhance the adhesion of the deposited seeds to the target substrate.